A multiple-input-multiple-output (MIMO) wireless network is a communication system that generally includes an access point (AP) having multiple antennas communicatively coupled to multiple receiving stations (STA). To support downlink multi-user downlink MIMO network, the access point (AP) may need to schedule multiple packets destined for the multiple stations for simultaneous transmission. Existing IEEE 802.11 standards do not support downlink multi-user MIMO. As such, current access points (AP) choose the first packet or the first aggregate packet in the access point (AP) queue for transmission.
In current IEEE 802.11 stations (STA) implementation, packets are pushed into first-in-first-out (FIFO) queues sequentially. The first packet in each access category (AC) queue participates in an internal contention. The winner of the internal contention then goes on to participate in external contention. There is no mechanism provided in the IEEE 802.11 standard to support downlink spatial division multiple access (SDMA), where the access point (AP) needs to choose multiple packets to transmit simultaneously.